Crosslinkable and crosslinked compositions

Abstract

Crosslinkable compositions, crosslinked compositions, articles containing these compositions, and methods of making the articles are provided. The crosslinkable compositions, which include two (meth)acrylate copolymers plus a tackifier, are used to form the crosslinked compositions upon exposure to ultraviolet radiation. The crosslinked compositions can function as pressure-sensitive adhesives. The crosslinkable compositions are well suited for use with hot melt processing methods.

We claim: 
     
       1. A crosslinkable composition comprising:
 1) at least different two (meth)acrylate copolymers comprising
 a) a first (meth)acrylate copolymer having a weight average molecular weight greater than or equal to at least 100,000 Daltons, wherein the first (meth)acrylate copolymer is a reaction product of a first monomer mixture comprising
 (i) an alkyl (meth)acrylate; and 
 (ii) an optional UV crosslinking monomer having an aromatic ketone group that is crosslinkable when exposed to ultraviolet radiation, wherein the UV crosslinking monomer is present in an amount in a range of 0 to 0.3 mole percent based on total moles of monomer in the first monomer mixture; and 
 
 b) a second (meth)acrylate copolymer having a weight average molecular weight greater than or equal to 100,000 Daltons, wherein the second (meth)acrylate copolymer is a reaction product of a second monomer mixture comprising
 (i) an alkyl (meth)acrylate; and 
 (ii) a UV crosslinking monomer having an aromatic ketone group that is crosslinkable when exposed to ultraviolet radiation, wherein the UV crosslinking monomer is present in an amount equal to at least 1 mole percent based on total moles of monomer in the second monomer mixture, 
 
 
 wherein total weight of the (meth)acrylate copolymers in kilograms divided by total moles of UV crosslinker used to form the (meth)acrylate copolymers is no greater than 150 kilograms per mole; and 
 2) a tackifier in an amount equal to at least 20 weight percent based on a total weight of solids in the crosslinkable composition. 
 
     
     
       2. The crosslinkable composition of  claim 1 , wherein the first (meth)acrylate copolymer is present in an amount in a range of 80 to 98 weight percent and the second (meth)acrylate copolymer is present in an amount in a range of 2 to 20 weight percent based on a total weight of (meth)acrylate copolymers in the crosslinkable composition. 
     
     
       3. The crosslinkable composition of  claim 1 , wherein the weight average molecular weight of the second (meth)acrylate copolymer is greater than 500,000 Daltons. 
     
     
       4. The crosslinkable composition of  claim 1 , wherein the UV crosslinking monomer in the second monomer mixture and the optional UV crosslinking monomer in the first monomer mixture is a benzophenone-containing monomer. 
     
     
       5. The crosslinkable composition of  claim 1 , wherein the first monomer mixture further comprises a polar monomer, the second monomer mixture further comprises a polar monomer, or both. 
     
     
       6. The crosslinkable composition of  claim 1 , wherein the UV crosslinking monomer in the first monomer mixture is present in an amount in a range of 0.01 to 0.3 based on total moles of monomer in the first monomer mixture. 
     
     
       7. The crosslinkable composition of  claim 1 , wherein the first reaction mixture further comprises a polar monomer having an acid group and the second monomer mixture further comprises a polar monomer having a basic group or wherein the first reaction mixture further comprises a polar monomer having a basic group and the second monomer mixture further comprises a polar monomer having an acidic group. 
     
     
       8. An article comprising:
 a substrate; and 
 a coating of a crosslinkable composition positioned adjacent to the substrate, the crosslinkable composition comprising
 1) at least two different (meth)acrylate copolymers comprising
 a) a first (meth)acrylate copolymer having a weight average molecular weight greater than or equal to at least 100,000 Daltons, wherein the first (meth)acrylate copolymer is a reaction product of a first monomer mixture comprising
 (i) an alkyl (meth)acrylate; and 
 (ii) an optional UV crosslinking monomer having an aromatic ketone group that is crosslinkable when exposed to ultraviolet radiation, wherein the UV crosslinking monomer is present in an amount in a range of 0 to 0.3 mole percent based on total moles of monomer in the first monomer mixture; and 
 
 b) a second (meth)acrylate copolymer having a weight average molecular weight greater than or equal to 100,000 Daltons, wherein the second (meth)acrylate copolymer is a reaction product of a second monomer mixture comprising
 (i) an alkyl (meth)acrylate; and 
 (ii) a UV crosslinking monomer having an aromatic ketone group that is crosslinkable when exposed to ultraviolet radiation, wherein the UV crosslinking monomer is present in an amount equal to at least 1 mole percent based on total moles of monomer in the second monomer mixture, 
 
 
 wherein a total weight of the (meth)acrylate copolymers in kilograms divided by a total moles of UV crosslinker in the (meth)acrylate copolymers is no greater than 150 kilograms per mole; and 
 2) a tackifier in an amount equal to at least 20 weight percent based on a total weight of solids in the crosslinkable composition. 
 
 
     
     
       9. The article of  claim 8 , wherein the weight average molecular weight of the second (meth)acrylate copolymer is greater than 500,000 Daltons. 
     
     
       10. A crosslinked composition comprising a reaction product of a crosslinkable composition exposed to ultraviolet radiation, the crosslinkable composition comprising:
 1) at least two different (meth)acrylate copolymers comprising
 a) a first (meth)acrylate copolymer having a weight average molecular weight greater than or equal to at least 100,000 Daltons, wherein the first (meth)acrylate copolymer is a reaction product of a first monomer mixture comprising
 (i) an alkyl (meth)acrylate; and 
 (ii) an optional UV crosslinking monomer having an aromatic ketone group that is crosslinkable when exposed to ultraviolet radiation, wherein the UV crosslinking monomer is present in an amount in a range of 0 to 0.3 mole percent based on total moles of monomer in the first monomer mixture; and 
 
 b) a second (meth)acrylate copolymer having a weight average molecular weight greater than or equal to 100,000 Daltons, wherein the second (meth)acrylate copolymer is a reaction product of a second monomer mixture comprising
 (i) an alkyl (meth)acrylate; and 
 (ii) a UV crosslinking monomer having an aromatic ketone group that is crosslinkable when exposed to ultraviolet radiation, wherein the UV crosslinking monomer is present in an amount equal to at least 1 mole percent based on total moles of monomer in the second monomer mixture, 
 
 
 wherein a total weight of the (meth)acrylate copolymers in kilograms divided by a total moles of UV crosslinker in the (meth)acrylate copolymers is no greater than 150 kilograms per mole; and 
 2) a tackifier in an amount equal to at least 20 weight percent based on a total weight of solids in the crosslinkable composition. 
 
     
     
       11. The crosslinked composition of  claim 10 , wherein the weight average molecular weight of the second (meth)acrylate copolymer is greater than 500,000 Daltons. 
     
     
       12. The crosslinked composition of  claim 10 , wherein the first monomer mixture further comprises a polar monomer, the second monomer mixture further comprises a polar monomer, or both. 
     
     
       13. An article comprising:
 a substrate; and 
 a coating of a crosslinked composition positioned adjacent to the substrate, the crosslinked composition comprising a reaction product of a crosslinkable composition exposed to ultraviolet radiation, the crosslinkable composition comprising: 
 1) at least two different (meth)acrylate copolymers comprising
 a) a first (meth)acrylate copolymer having a weight average molecular weight greater than or equal to at least 100,000 Daltons, wherein the first (meth)acrylate copolymer is a reaction product of a first monomer mixture comprising
 (i) an alkyl (meth)acrylate; and 
 (ii) an optional UV crosslinking monomer having an aromatic ketone group that is crosslinkable when exposed to ultraviolet radiation, wherein the UV crosslinking monomer is present in an amount in a range of 0 to 0.3 mole percent based on total moles of monomer in the first monomer mixture; and 
 
 b) a second (meth)acrylate copolymer having a weight average molecular weight greater than or equal to 100,000 Daltons, wherein the second (meth)acrylate copolymer is a reaction product of a second monomer mixture comprising
 (i) an alkyl (meth)acrylate; and 
 (ii) a UV crosslinking monomer having an aromatic ketone group that is crosslinkable when exposed to ultraviolet radiation, wherein the UV crosslinking monomer is present in an amount equal to at least 1 mole percent based on total moles of monomer in the second monomer mixture, 
 
 
 wherein a total weight of the (meth)acrylate copolymers in kilograms divided by a total moles of UV crosslinker in the (meth)acrylate copolymers is no greater than 150 kilograms per mole; and 
 2) a tackifier in an amount equal to at least 20 weight percent based on a total weight of solids in the crosslinkable composition. 
 
     
     
       14. The article of  claim 13 , wherein the weight average molecular weight of the second (meth)acrylate copolymer is greater than 500,000 Daltons. 
     
     
       15. A method of preparing an article, the method comprising:
 providing a substrate; 
 positioning a crosslinkable composition adjacent to the substrate, wherein the crosslinkable composition comprises
 1) at least two different (meth)acrylate copolymers comprising
 a) a first (meth)acrylate copolymer having a weight average molecular weight greater than or equal to at least 100,000 Daltons, wherein the first (meth)acrylate copolymer is a reaction product of a first monomer mixture comprising
 (i) an alkyl (meth)acrylate; and 
 (ii) an optional UV crosslinking monomer having an aromatic ketone group that is crosslinkable when exposed to ultraviolet radiation, wherein the UV crosslinking monomer is present in an amount in a range of 0 to 0.3 mole percent based on total moles of monomer in the first monomer mixture; and 
 
 b) a second (meth)acrylate copolymer having a weight average molecular weight greater than or equal to 100,000 Daltons, wherein the second (meth)acrylate copolymer is a reaction product of a second monomer mixture comprising
 (i) an alkyl (meth)acrylate; and 
 (ii) a UV crosslinking monomer having an aromatic ketone group that is crosslinkable when exposed to ultraviolet radiation, wherein the UV crosslinking monomer is present in an amount equal to at least 1 mole percent based on total moles of monomer in the second monomer mixture, 
 
 
 wherein a total weight of the (meth)acrylate copolymers in kilograms divided by a total moles of UV crosslinker in the (meth)acrylate copolymers is no greater than 150 kilograms per mole; and 
 2) a tackifier in an amount equal to at least 20 weight percent based on a total weight of solids in the crosslinkable composition; and 
 
 exposing the crosslinkable composition to ultraviolet light to form a crosslinked composition.